Polycarbonates are useful in the manufacture of articles and components for a wide range of applications, from automotive parts to electronic appliances. Polycarbonate resins exhibit higher levels of heat resistance, impact resistance, and electric properties as well as good dimensional stability. Polycarbonate resins, however, suffer from high melt viscosity and poor organic solvent resistance as well as poor abrasion/friction properties, and their use in limited in the fields wherein such properties are beneficial.
In order to solve one or more of these problems, various attempts have been attempted wherein the polycarbonate is mixed with a polyolefin. Such resin compositions, however, often fail to be practical due to the low compatibility of the polycarbonate and the polyolefin that often results in delamination, and hence, in poor appearance of the product when a molded article is produced from the resin composition by such means as injection molding. Various attempts have been made to improve the compatibility of the polycarbonate and the polyolefin by incorporating into the polycarbonate-polyolefin resin composition a polystyrene-polyolefin copolymer such as SEBS (styrene-ethylene/butylene-styrene copolymer), SEP (styrene-ethylene/propylene), or the like. However, the incorporated polystyrene-polyolefin copolymer is of elastomeric nature, and the resulting resin composition generally suffers from poor heat resistance and flexural rigidity.
Other prior art solutions have included a polycarbonate-polyolefin resin wherein the polycarbonate has a terminal carboxyl group and a polypropylene having epoxy group or wherein the polycarbonate-polyolefin resin further includes a polycarbonate having a terminal hydroxyl group and polypropylene having carboxyl group. These compositions do not generally undergo delamination, and the articles prepared from such compositions exhibit improved mechanical strength and organic solvent resistance as well as improved outer appearance with no delamination. However, the carboxyl- and the hydroxyl-containing polycarbonates used for constituting such resins are those respectively prepared by adding a special monomer in the polymerization stage of the polycarbonate resin, and production of such resins generally requires a polycarbonate polymerization installation. Therefore, processes utilizing such components result in a heavy financial burden to resin manufacturers that do not have such polycarbonate polymerization installation. Accordingly, production of the polycarbonate-polyolefin resin that includes such a resin component is difficult.
Attempts have also been made to add a fluororesin such as polytetrafluoroethylene to a polycarbonate resin to thereby improve friction/abrasion properties. Such compositions have improved wear resistant properties in addition to the above-described excellent properties inherent to the polycarbonate resin. However, the fluororesin used in such composition is rather expensive, and upon thermal disposal of the resin composition, the fluororesin often generates toxic gases. In view of such situation, there has been a strong demand for a polycarbonate based resin slide material that may substitute for a polycarbonate/fluororesin based resin composition.
An alternative solution has been the use of polyolefin resins, and in particular, high-density polyethylene, low-density polyethylene, and straight-chain low-density polyethylene, that are often inexpensive and/or excellent in friction/abrasion properties. Such polyolefin resins are, however, inferior to the polycarbonate resins in their heat resistance, flexural rigidity, and flame retardancy. Therefore, it has been difficult to use a polyolefin resin in an application wherein a polycarbonate/fluororesin based resin composition is used. In view of such situation, various attempts have been made to mix the polycarbonate with the polyethylene in order to develop a resin composition that is able to maintain the improved heat resistance, impact resistance, and/or flame retardancy of the polycarbonate resin with the improved friction/abrasion properties of the polyolefin. In spite of such attempts, the markedly poor compatibility of the polycarbonate with the polyethylene often results in delamination of the molded article, especially upon frictional contact or under abrasion, leading to poor abrasion properties.
As a result, the process used to form these polycarbonate/polyolefin compositions can suffer from reduced yields. The prior art process is a two-step process wherein an intermediary polyolefin is formed, with the resulting intermediary then mixed with the polycarbonate and extruded to form the resin composition. Since the prior art process for forming the intermediary polyolefin requires a second step using additional equipment and manufacturing time, the prior art two-step process requires additional equipment costs and energy costs to form the resin composition.
Accordingly, it would be beneficial to provide a thermoplastic material that offers enhanced wear characteristics. It would also be beneficial to provide a process for making a resin composition that offered improved yields and/or reduced production costs as compared to prior art processes. It would also be beneficial to provide a molded article made from a resin composition wherein the molded article has improved wear characteristics.